系列目录
分布式事务（一）原理概览
分布式事务（二）JTA规范
分布式事务（三）mysql对XA协议的支持
分布式事务（四）简单样例
分布式事务（五）源码详解
分布式事务（六）总结提高
引子
本节我们将会从上一节的”简单样例“入手：Spring Boot+Atomikos(TM)+Mybatis(ORM)+Mysql(DB)，深入源码，看看这个分布式事务是怎么定义、执行的。
先来回忆一下第二节讲的JTA规范，如下图。Atomikos是什么角色？起到什么作用？
角色：
Atomikos根本上是一个事务管理器(TM)也就是JTA模型的核心，上图扇形的中心位置。
作用：
TM调用 【Resource Manager资源管理器】 的XAResource接口来实现事务操作。
TM依赖 【Application Server应用服务器】 的TransactionManager接口当然如果服务器不支持事务管理，自然也就只能使用第三方包，例如Atomikos。
TM依赖 【Application应用程序】 设置事务边界、属性，application调用UserTransaction接口控制事务开始、提交、回滚。
一、bean定义
1.1 JtaTransactionManager
org.springframework.transaction.jta.JtaTransactionManager类是spring提供的分布式事务管理器。
JtaTransactionManager类图如下：
实现了接口如下：
- PlatformTransactionManager ：获取事务，提交事务，回滚事务
- TransactionFactory：创建事务
- InitializingBean：初始化bean
JtaTransactionManager实现了InitializingBean接口的afterPropertiesSet()方法，处于bean生命周期的容器初始化->实例化期->初始化中期，如下图：
下面我们看一下JtaTransactionManager在bean初始化中期InitializingBean接口的afterPropertiesSet()做了什么：
1 /**
2 * Initialize the UserTransaction as well as the TransactionManager handle.
3 * @see #initUserTransactionAndTransactionManager() 4 */ 5 @Override 6 public void afterPropertiesSet() throws TransactionSystemException { 7 initUserTransactionAndTransactionManager(); 8 checkUserTransactionAndTransactionManager(); 9 initTransactionSynchronizationRegistry(); 10 }
-
1.initUserTransactionAndTransactionManager：初始化UserTransaction和TransactionManager接口。主要是如果没有定义的话，可以支持JNDI。
-
2.checkUserTransactionAndTransactionManager：校验2个接口是否存在。UserTransaction必须定义，TransactionManager可以不定义。
源码如下：
对应控制台打印：
o.s.t.jta.JtaTransactionManager : Using JTA UserTransaction: com.atomikos.icatch.jta.UserTransactionImp@614aeccc
o.s.t.jta.JtaTransactionManager : Using JTA TransactionManager: com.atomikos.icatch.jta.UserTransactionManager@5116ac09
- 3.initTransactionSynchronizationRegistry：初始化事务同步注册，这个不使用JNDI的话没啥用。
上一节分布式事务（三）简单样例中我们配置了JtaTransactionManagerConfig类，如下：
1 package study.config.datasource;
2
3 import com.atomikos.icatch.jta.UserTransactionImp; 4 import com.atomikos.icatch.jta.UserTransactionManager; 5 import org.springframework.context.annotation.Bean; 6 import org.springframework.context.annotation.Configuration; 7 import org.springframework.transaction.jta.JtaTransactionManager; 8 9 import javax.transaction.UserTransaction; 10 11 /** 12 * 事务管理器配置类 13 * 14 * @author denny 15 */ 16 @Configuration 17 public class JtaTransactionManagerConfig { 18 19 @Bean(name = "atomikosTransactionManager") 20 public JtaTransactionManager regTransactionManager() { 21 UserTransactionManager userTransactionManager = new UserTransactionManager(); 22 UserTransaction userTransaction = new UserTransactionImp(); 23 return new JtaTransactionManager(userTransaction, userTransactionManager); 24 } 25 }
如上图，我们定义了一个name = "atomikosTransactionManager"的bean,具体类型为JtaTransactionManager。其中构造了2个实现类UserTransactionImp（javax.transaction.UserTransaction接口）、UserTransactionManager（javax.transaction.TransactionManager接口）。并用这2个实现类构造了一个JtaTransactionManager。
1.UserTransaction接口
提供给用户操控事务的：开启，提交，回滚等等。源码如下：
2 TransactionManager接口
源码如下：
相比UserTransaction，TransactionManager接口多了接口的挂起、恢复、获取事务3个接口。这3个方法明显是留给系统自己调用的。
1.2 AtomikosDataSourceBean
Spring 为Atomikos定制了一个org.springframework.boot.jta.atomikos.AtomikosDataSourceBean，提供了bean生命周期的一些接口：
- BeanNameAware：设置bean名称
- InitializingBean：初始化bean
- DisposableBean:销毁bean
我们只需要定义这个bean即可轻松使得spring来维护。
com.atomikos.jdbc.AtomikosDataSourceBean类图如下:
其中核心接口：
DataSource接口：getConnection获取数据库连接
ConnectionPoolProperties接口：用于载入连接池的属性
二、源码剖析
2.1 自动配置类
老套路哈，spring boot就这么点花花肠子，既然使用@Transactional这种注解的方式，那么我们就从springboot 容器启动时的自动配置载入（spring boot容器启动详解）开始看。在/META-INF/spring.factories中配置文件中查找，如下图：
载入2个关于事务的自动配置类：
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,
由于本文是分布式事务，故2个配置文件都生效了，我们先看JtaAutoConfiguration
2.2 JtaAutoConfiguration
1 /** 2 * {@link EnableAutoConfiguration Auto-configuration} for JTA. 3 * 4 * @author Josh Long 5 * @author Phillip Webb 6 * @since 1.2.0 7 */ 8 @ConditionalOnClass(javax.transaction.Transaction.class) 9 @ConditionalOnProperty(prefix = "spring.jta", value = "enabled", matchIfMissing = true) 10 @AutoConfigureBefore({ XADataSourceAutoConfiguration.class, 11 ActiveMQAutoConfiguration.class, ArtemisAutoConfiguration.class, 12 HibernateJpaAutoConfiguration.class }) 13 @Import({ JndiJtaConfiguration.class, BitronixJtaConfiguration.class, 14 AtomikosJtaConfiguration.class, NarayanaJtaConfiguration.class }) 15 @EnableConfigurationProperties(JtaProperties.class) 16 public class JtaAutoConfiguration { 17 18 }
如上，JtaAutoConfiguration这个类竟然是个空壳，只有一堆注解，挑几个重要的讲一讲：
1.@ConditionalOnClass(javax.transaction.Transaction.class)：代表类路径下存在javax.transaction.Transaction.class这个类，那么JtaAutoConfiguration生效。
2.@ConditionalOnProperty(prefix = "spring.jta", value = "enabled", matchIfMissing = true)，自动开启spring.jta.enabled=true.
3.@Import({ JndiJtaConfiguration.class, BitronixJtaConfiguration.class, AtomikosJtaConfiguration.class, NarayanaJtaConfiguration.class }),又是spring套路哈，用来导入类。这里导入了4个配置类，可见支持4种第三方事务管理器。AtomikosJtaConfiguration.class自然就是Atomikos了。
AtomikosJtaConfiguration.class这个配置类
1 @Configuration 2 @EnableConfigurationProperties({ AtomikosProperties.class, JtaProperties.class }) 3 @ConditionalOnClass({ JtaTransactionManager.class, UserTransactionManager.class }) 4 @ConditionalOnMissingBean(PlatformTransactionManager.class) 5 class AtomikosJtaConfiguration { 6 7 private final JtaProperties jtaProperties; 8 9 private final TransactionManagerCustomizers transactionManagerCustomizers; 10 11 AtomikosJtaConfiguration(JtaProperties jtaProperties, 12 ObjectProvidertransactionManagerCustomizers) { 13 this.jtaProperties = jtaProperties; 14 this.transactionManagerCustomizers = transactionManagerCustomizers 15 .getIfAvailable(); 16 } 17 18 @Bean(initMethod = "init", destroyMethod = "shutdownForce") 19 @ConditionalOnMissingBean(UserTransactionService.class) 20 public UserTransactionServiceImp userTransactionService( 21 AtomikosProperties atomikosProperties) { 22 Properties properties = new Properties(); 23 if (StringUtils.hasText(this.jtaProperties.getTransactionManagerId())) { 24 properties.setProperty("com.atomikos.icatch.tm_unique_name", 25 this.jtaProperties.getTransactionManagerId()); 26 } 27 properties.setProperty("com.atomikos.icatch.log_base_dir", getLogBaseDir()); 28 properties.putAll(atomikosProperties.asProperties()); 29 return new UserTransactionServiceImp(properties); 30 } 31 32 private String getLogBaseDir() { 33 if (StringUtils.hasLength(this.jtaProperties.getLogDir())) { 34 return this.jtaProperties.getLogDir(); 35 } 36 File home = new ApplicationHome().getDir(); 37 return new File(home, "transaction-logs").getAbsolutePath(); 38 } 39 40 @Bean(initMethod = "init", destroyMethod = "close") 41 @ConditionalOnMissingBean 42 public UserTransactionManager atomikosTransactionManager( 43 UserTransactionService userTransactionService) throws Exception { 44 UserTransactionManager manager = new UserTransactionManager(); 45 manager.setStartupTransactionService(false); 46 manager.setForceShutdown(true); 47 return manager; 48 } 49 50 @Bean 51 @ConditionalOnMissingBean(XADataSourceWrapper.class) 52 public AtomikosXADataSourceWrapper xaDataSourceWrapper() { 53 return new AtomikosXADataSourceWrapper(); 54 } 55 56 @Bean 57 @ConditionalOnMissingBean 58 public static AtomikosDependsOnBeanFactoryPostProcessor atomikosDependsOnBeanFactoryPostProcessor() { 59 return new AtomikosDependsOnBeanFactoryPostProcessor(); 60 } 61 62 @Bean 63 public JtaTransactionManager transactionManager(UserTransaction userTransaction, 64 TransactionManager transactionManager) { 65 JtaTransactionManager jtaTransactionManager = new JtaTransactionManager( 66 userTransaction, transactionManager); 67 if (this.transactionManagerCustomizers != null) { 68 this.transactionManagerCustomizers.customize(jtaTransactionManager); 69 } 70 return jtaTransactionManager; 71 } 72 73 @Configuration 74 @ConditionalOnClass(Message.class) 75 static class AtomikosJtaJmsConfiguration { 76 77 @Bean 78 @ConditionalOnMissingBean(XAConnectionFactoryWrapper.class) 79 public AtomikosXAConnectionFactoryWrapper xaConnectionFactoryWrapper() { 80 return new AtomikosXAConnectionFactoryWrapper(); 81 } 82 83 } 84 85 }
2.3 TransactionAutoConfiguration
这里和本地事务分析过程一致，就不再重复，飞机票spring事务详解（三）源码详解，一直看到第二节结束.这里只截个图：
最终源码调用具体事务管理器的PlatformTransactionManager接口的3个方法：
1 public interface PlatformTransactionManager {
2 // 获取事务状态 3 TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException; 4 // 事务提交 5 void commit(TransactionStatus status) throws TransactionException; 6 // 事务回滚 7 void rollback(TransactionStatus status) throws TransactionException; 8 }
三、核心源码
核心实现类图：
如上提所示，PlatformTransactionManager顶级接口定义了最核心的事务管理方法，下面一层是AbstractPlatformTransactionManager抽象类，实现了PlatformTransactionManager接口的方法并定义了一些抽象方法，供子类拓展。最下面一层是2个经典事务管理器：
1.DataSourceTransactionmanager: 即本地单资源事务管理器。
2.JtaTransactionManager: 即多资源事务管理器（又叫做分布式事务管理器），其实现了JTA规范，使用XA协议进行两阶段提交。
我们这里自然是JTA分布式环境，我们只需要从JtaTransactionManager这个实现类入手即可。
3.1 getTransaction获取事务
AbstractPlatformTransactionManager实现了getTransaction()方法如下：
1 @Override 2 public final TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException { 3 Object transaction = doGetTransaction(); 4 5 // Cache debug flag to avoid repeated checks. 6 boolean debugEnabled = logger.isDebugEnabled(); 7 8 if (definition == null) { 9 // Use defaults if no transaction definition given. 10 definition = new DefaultTransactionDefinition(); 11 } 12 // 如果当前已经存在事务 13 if (isExistingTransaction(transaction)) { 14 // 根据不同传播机制不同处理 15 return handleExistingTransaction(definition, transaction, debugEnabled); 16 } 17 18 // 超时不能小于默认值 19 if (definition.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) { 20 throw new InvalidTimeoutException("Invalid transaction timeout", definition.getTimeout()); 21 } 22 23 // 当前不存在事务，传播机制=MANDATORY（支持当前事务，没事务报错），报错 24 if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) { 25 throw new IllegalTransactionStateException( 26 "No existing transaction found for transaction marked with propagation 'mandatory'"); 27 }// 当前不存在事务，传播机制=REQUIRED/REQUIRED_NEW/NESTED,这三种情况，需要新开启事务，且加上事务同步 28 else if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED || 29 definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW || 30 definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) { 31 SuspendedResourcesHolder suspendedResources = suspend(null); 32 if (debugEnabled) { 33 logger.debug("Creating new transaction with name [" + definition.getName() + "]: " + definition); 34 } 35 try {// 是否需要新开启同步// 开启// 开启 36 boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER); 37 DefaultTransactionStatus status = newTransactionStatus( 38 definition, transaction, true, newSynchronization, debugEnabled, suspendedResources); 39 doBegin(transaction, definition);// 开启新事务 40 prepareSynchronization(status, definition);//预备同步 41 return status; 42 } 43 catch (RuntimeException ex) { 44 resume(null, suspendedResources); 45 throw ex; 46 } 47 catch (Error err) { 48 resume(null, suspendedResources); 49 throw err; 50 } 51 } 52 else { 53 // 当前不存在事务当前不存在事务，且传播机制=PROPAGATION_SUPPORTS/PROPAGATION_NOT_SUPPORTED/PROPAGATION_NEVER，这三种情况，创建“空”事务:没有实际事务，但可能是同步。警告：定义了隔离级别，但并没有真实的事务初始化，隔离级别被忽略有隔离级别但是并没有定义实际的事务初始化，有隔离级别但是并没有定义实际的事务初始化， 54 if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT && logger.isWarnEnabled()) { 55 logger.warn("Custom isolation level specified but no actual transaction initiated; " + 56 "isolation level will effectively be ignored: " + definition); 57 } 58 boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS); 59 return prepareTransactionStatus(definition, null, true, newSynchronization, debugEnabled, null); 60 } 61 }
上图核心步骤就是：
- 1.doGetTransaction()：获取事务
- 2.doBegin：准备工作
3.1.1 JtaTransactionManager的doGetTransaction()
其实也就是把UserTransaction封装成一个JtaTransactionObject返回。
1 @Override 2 protected Object doGetTransaction() { 3 UserTransaction ut = getUserTransaction(); 4 if (ut == null) { 5 throw new CannotCreateTransactionException("No JTA UserTransaction available - " + 6 "programmatic PlatformTransactionManager.getTransaction usage not supported"); 7 } 8 if (!this.cacheUserTransaction) { 9 ut = lookupUserTransaction( 10 this.userTransactionName != null ? this.userTransactionName : DEFAULT_USER_TRANSACTION_NAME); 11 } 12 return doGetJtaTransaction(ut); 13 } 14 15 /** 16 * Get a JTA transaction object for the given current UserTransaction. 17 *Subclasses can override this to provide a JtaTransactionObject
18 * subclass, for example holding some additional JTA handle needed. 19 * @param ut the UserTransaction handle to use for the current transaction 20 * @return the JtaTransactionObject holding the UserTransaction 21 */ 22 protected JtaTransactionObject doGetJtaTransaction(UserTransaction ut) { 23 return new JtaTransactionObject(ut); 24 }
3.1.2 JtaTransactionManager.doBegin
1 @Override 2 protected void doBegin(Object transaction, TransactionDefinition definition) { 3 JtaTransactionObject txObject = (JtaTransactionObject) transaction; 4 try { 5 doJtaBegin(txObject, definition); 6 } 7 catch (NotSupportedException ex) { 8 // assume nested transaction not supported 9 throw new NestedTransactionNotSupportedException( 10 "JTA implementation does not support nested transactions", ex); 11 } 12 catch (UnsupportedOperationException ex) { 13 // assume nested transaction not supported 14 throw new NestedTransactionNotSupportedException( 15 "JTA implementation does not support nested transactions", ex); 16 } 17 catch (SystemException ex) { 18 throw new CannotCreateTransactionException("JTA failure on begin", ex); 19 } 20 }
调用JtaTransactionManager.doJtaBegin：
1 protected void doJtaBegin(JtaTransactionObject txObject, TransactionDefinition definition) 2 throws NotSupportedException, SystemException { 3 4 applyIsolationLevel(txObject, definition.getIsolationLevel()); 5 int timeout = determineTimeout(definition); 6 applyTimeout(txObject, timeout); 7 txObject.getUserTransaction().begin(); 8 }
UserTransactionImp.begin->TransactionManagerImp.begin
1 public void begin ( int timeout ) throws NotSupportedException, 2 SystemException 3 { 4 CompositeTransaction ct = null; 5 ResumePreviousTransactionSubTxAwareParticipant resumeParticipant = null; 6 7 ct = compositeTransactionManager.getCompositeTransaction(); 8 if ( ct != null && ct.getProperty ( JTA_PROPERTY_NAME ) == null ) { 9 LOGGER.logWarning ( "JTA: temporarily suspending incompatible transaction: " + ct.getTid() + 10 " (will be resumed after JTA transaction ends)" ); 11 ct = compositeTransactionManager.suspend(); 12 resumeParticipant = new ResumePreviousTransactionSubTxAwareParticipant ( ct ); 13 } 14 15 try { 16 ct = compositeTransactionManager.createCompositeTransaction ( ( ( long ) timeout ) * 1000 ); 17 if ( resumeParticipant != null ) ct.addSubTxAwareParticipant ( resumeParticipant ); 18 if ( ct.isRoot () && getDefaultSerial () ) 19 ct.getTransactionControl ().setSerial (); 20 ct.setProperty ( JTA_PROPERTY_NAME , "true" ); 21 } catch ( SysException se ) { 22 String msg = "Error in begin()"; 23 LOGGER.logWarning( msg , se ); 24 throw new ExtendedSystemException ( msg , se 25 .getErrors () ); 26 } 27 recreateCompositeTransactionAsJtaTransaction(ct); 28 }
createCompositeTransaction创建混合事务
1 public CompositeTransaction createCompositeTransaction ( long timeout ) throws SysException 2 { 3 Stack errors = new Stack(); 4 CompositeTransaction ct = null , ret = null; 5 // 获取当前线程绑定的事务 6 ct = getCurrentTx ();
// 当前线程不存在事务 7 if ( ct == null ) {
// 创建组合事务 8 ret = service_.createCompositeTransaction ( timeout ); 9 if(LOGGER.isInfoEnabled()){ 10 LOGGER.logInfo("createCompositeTransaction ( " + timeout + " ): " 11 + "created new ROOT transaction with id " + ret.getTid ()); 12 }
// 当前线程存在事务 13 } else { 14 if(LOGGER.isInfoEnabled()) LOGGER.logInfo("createCompositeTransaction ( " + timeout + " )");
// 创建子事务 15 ret = ct.getTransactionControl ().createSubTransaction (); 16 17 } 18 Thread thread = Thread.currentThread ();
// 绑定当前线程和事务的2个映射map 19 setThreadMappings ( ret, thread ); 20 21 return ret; 22 }
如果当前线程不存在事务，创建组合事务。如果当前线程存在事务，创建子事务。
调用TransactionServiceImp的createCompositeTransaction创建混合事务
1 public CompositeTransaction createCompositeTransaction ( long timeout ) throws SysException 2 { 3 if ( !initialized_ ) throw new IllegalStateException ( "Not initialized" ); 4 5 if ( maxNumberOfActiveTransactions_ >= 0 && 6 tidToTransactionMap_.size () >= maxNumberOfActiveTransactions_ ) { 7 throw new IllegalStateException ( "Max number of active transactions reached:" + maxNumberOfActiveTransactions_ ); 8 } 9 10 String tid = tidmgr_.get (); 11 Stack lineage = new Stack (); 12 //创建协调者 15 CoordinatorImp cc = createCC ( null, tid, true, false, timeout );
// 创建组合事务 16 CompositeTransaction ct = createCT ( tid, cc, lineage, false ); 17 return ct; 18 }
3.2 commit 提交事务
事务提交流程图如下：
AbstractPlatformTransactionManager的commit源码如下：
1 @Override
2 public final void commit(TransactionStatus status) throws TransactionException { 3 if (status.isCompleted()) {// 如果事务已完结，报错无法再次提交 4 throw new IllegalTransactionStateException( 5 "Transaction is already completed - do not call commit or rollback more than once per transaction"); 6 } 7 8 DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status; 9 if (defStatus.isLocalRollbackOnly()) {// 如果事务明确标记为回滚， 10 if (defStatus.isDebug()) { 11 logger.debug("Transactional code has requested rollback"); 12 } 13 processRollback(defStatus);//执行回滚 14 return; 15 }//如果不需要全局回滚时提交 且 全局回滚 16 if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) { 17 if (defStatus.isDebug()) { 18 logger.debug("Global transaction is marked as rollback-only but transactional code requested commit"); 19 }//执行回滚 20 processRollback(defStatus); 21 // 仅在最外层事务边界（新事务）或显式地请求时抛出“未期望的回滚异常” 23 if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) { 24 throw new UnexpectedRollbackException( 25 "Transaction rolled back because it has been marked as rollback-only"); 26 } 27 return; 28 } 29 // 执行提交事务 30 processCommit(defStatus); 31 }
如上图，各种判断：
- 1.如果事务明确标记为本地回滚，-》执行回滚
- 2.如果不需要全局回滚时提交 且 全局回滚-》执行回滚
- 3.提交事务，核心方法processCommit()
processCommit如下：
1 private void processCommit(DefaultTransactionStatus status) throws TransactionException {
2 try { 3 boolean beforeCompletionInvoked = false; 4 try {//3个前置操作 5 prepareForCommit(status); 6 triggerBeforeCommit(status); 7 triggerBeforeCompletion(status); 8 beforeCompletionInvoked = true;//3个前置操作已调用 9 boolean globalRollbackOnly = false;//新事务 或 全局回滚失败 10 if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) { 11 globalRollbackOnly = status.isGlobalRollbackOnly(); 12 }//1.有保存点，即嵌套事务 13 if (status.hasSavepoint()) { 14 if (status.isDebug()) { 15 logger.debug("Releasing transaction savepoint"); 16 }//释放保存点 17 status.releaseHeldSavepoint(); 18 }//2.新事务 19 else if (status.isNewTransaction()) { 20 if (status.isDebug()) { 21 logger.debug("Initiating transaction commit"); 22 }//调用事务处理器提交事务 23 doCommit(status); 24 } 25 // 3.非新事务，且全局回滚失败，但是提交时没有得到异常，抛出异常 27 if (globalRollbackOnly) { 28 throw new UnexpectedRollbackException( 29 "Transaction silently rolled back because it has been marked as rollback-only"); 30 } 31 } 32 catch (UnexpectedRollbackException ex) { 33 // 触发完成后事务同步，状态为回滚 34 triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK); 35 throw ex; 36 }// 事务异常 37 catch (TransactionException ex) { 38 // 提交失败回滚 39 if (isRollbackOnCommitFailure()) { 40 doRollbackOnCommitException(status, ex); 41 }// 触发完成后回调，事务同步状态为未知 42 else { 43 triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN); 44 } 45 throw ex; 46 }// 运行时异常 47 catch (RuntimeException ex) {
// 如果3个前置步骤未完成，调用前置的最后一步操作 48 if (!beforeCompletionInvoked) { 49 triggerBeforeCompletion(status); 50 }// 提交异常回滚 51 doRollbackOnCommitException(status, ex); 52 throw ex; 53 }// 其它异常 54 catch (Error err) {
// 如果3个前置步骤未完成，调用前置的最后一步操作 55 if (!beforeCompletionInvoked) { 56 triggerBeforeCompletion(status); 57 }// 提交异常回滚 58 doRollbackOnCommitException(status, err); 59 throw err; 60 } 61 62 // Trigger afterCommit callbacks, with an exception thrown there 63 // propagated to callers but the transaction still considered as committed. 64 try { 65 triggerAfterCommit(status); 66 } 67 finally { 68 triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED); 69 } 70